S129: TAKEAIM LEUKEMIA- A PHASE 1/2A STUDY OF THE IRAK4 INHIBITOR EMAVUSERTIB (CA-4948) AS MONOTHERAPY OR IN COMBINATION WITH AZACITIDINE OR VENETOCLAX IN RELAPSED/REFRACTORY AML OR MDS
Authors: G. Garcia-Manero, E. S. Winer, D. J. DeAngelo, S. Tarantolo, D. A. Sallman, J. Dugan, S. Groepper, A. Giagounidis, K. Götze, K. H. Metzeler, C.-C. Li, L. Zhou, E. Martinez, M. Lane, R. von Roemeling, M. Bohme, A. S. Kubasch, A. Verma, U. Platzbecker
Journal: HemaSphere (2022)

Background: Emavusertib (CA-4948) is a novel oral inhibitor of interleukin-1 receptor-associated kinase 4 (IRAK4) and FLT3. IRAK4 is critical in triggering inflammation, oncogenesis, and survival of cancer cells. Genetic mutations in the splicing factors SF3B1 and U2AF1 drive overexpression of a highly active long isoform of IRAK4 and have been associated with disease progression and poor prognosis of high-risk myelodysplastic syndrome (HR-MDS) and acute myeloid leukemia (AML). Aims: Assessment of safety, clinical activity, and Recommended Phase 2 Dose (RP2D) of emavusertib as monotherapy or in combination with azacitidine (AZA) or venetoclax (VEN). Methods: This is an open-label, phase 1/2a dose escalation and cohort expansion trial (NCT04278768). In phase 1 Dose Escalation, patients with R/R AML or HR-MDS are treated with emavusertib monotherapy. Phase 1b includes 2 arms of combination therapy: emavusertib + AZA and emavusertib + VEN. The primary objectives of this study are to assess the safety, clinical activity, and identify the RP2D of emavusertib as monotherapy or in combination with AZA or VEN in R/R AML or HR-MDS. The Phase 2a Dose Expansion includes patients for emavusertib monotherapy: R/R AML with FLT3 mutation, or AML and HR-MDS R/R to HMA with U2AF1 or SF3B1 mutations. Results: As of December 16th, 2021, 49 patients have been treated in the phase 1 portion, of whom 43 started by September 30th, allowing 2 on-study disease assessments. The median number of prior therapies was 2 (range 1-5). Four monotherapy dose levels of emavusertib were tested (200 to 500 mg orally BID). No dose-limiting toxicities were observed at 200 mg and 300 mg BID. No Grade 4 or 5 treatment-related AEs (TRAEs) were reported, and all the TRAEs were manageable. Reversible, manageable Grade 3 rhabdomyolysis occurred in 1/26 (4%) patients at 300 mg BID, 2/17 (12%) at 400 mg BID, and 1/3 (33%) at 500 mg BID. RP2D was determined as 300 mg BID. Of 43 patients starting before Sept 30th, 2021, 14 had SF3B1, U2AF1 or FLT3 mutations and demonstrated more promising efficacy. In the 5 evaluable AML patients with spliceosome mutations, 40% reached CR/CRh (1 CR, 1 CRh), both with study duration >6 months. In the 7 spliceosome-mutated HR-MDS patients, 57% reached marrow CR, including 1 with RBC transfusion independence and 1 proceeding to HSCT. One of the three FLT3-mutated AML reached CR, and 2 became FLT3-negative. Among the 29 patients without SF3B1/U2AF1/FLT3 mutations, 1 reached CR and 2 PR. Phase 1b and Phase 2a are ongoing. RNA-seq on selected samples showed decrease in relative expression of IRAK4-long isoforms with response to emavusertib. Summary/Conclusion: Emavusertib is well tolerated and effective in heavily pretreated AML and HR-MDS patients, especially in those with U2AF1/SF3B1/FLT3 mutations. No dose-limiting myelosuppression was reported, suggesting emavusertib may be a candidate for combination therapy. Accrual of Phases 1b and 2a is ongoing.